How the TDEE calculator works
TDEE (total daily energy expenditure) is the number of calories you burn in a day. The calculator estimates it in two steps. First it calculates your basal metabolic rate (BMR) — the energy your body uses at complete rest — with the Mifflin-St Jeor equation, which was developed in 1990 and is the equation most dietitians use today:
Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5. Women: the same, but − 161 instead of + 5.
Then it multiplies BMR by an activity factor to account for exercise and daily movement.
- Sedentary (little or no exercise): × 1.2
- Light (exercise 1–3 days/week): × 1.375
- Moderate (exercise 3–5 days/week): × 1.55
- Active (exercise 6–7 days/week): × 1.725
- Very active (hard exercise plus a physical job): × 1.9
Worked example
A 45-year-old man who weighs 200 lb (90.7 kg), is 5′10″ (177.8 cm), and trains 3–5 days a week: BMR = 907 + 1,111 − 225 + 5 ≈ 1,798 kcal. Multiplied by 1.55 for moderate activity, his estimated TDEE is about 2,790 kcal per day. A cut at −500/day would be about 2,290 kcal; a lean build at +300/day about 3,090 kcal.
How to use the result
Treat the number as a starting estimate, not a measurement. Equations like Mifflin-St Jeor are accurate to within about 10% for most people, and the activity multipliers are the bigger source of error — most people overestimate how active they are. Eat at your target for two to three weeks while tracking your morning bodyweight, then adjust: if your weekly average weight isn’t moving the way you expect, change intake by 100–200 kcal/day and reassess.
After 40, preserving muscle matters as much as the calorie number. Pair any deficit with resistance training and an adequate protein intake so more of the weight you lose comes from fat rather than muscle.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is the energy your body uses at complete rest just to stay alive. TDEE adds everything else — exercise, walking, fidgeting, and digesting food — so it is always higher than BMR.
How many calories should I eat to lose a pound a week?
A deficit of roughly 500 kcal per day below your TDEE is the common rule of thumb for about 1 lb per week, though real-world loss varies and tends to slow over time as your body adapts.
Is the Mifflin-St Jeor equation accurate?
It is considered the most accurate of the common BMR equations for healthy adults and is usually within about 10% of measured values, but individuals can fall outside that range. Use real-world weight trends to fine-tune.
Does metabolism slow down after 40?
The equation subtracts a small amount per year of age, but much of the practical slowdown people notice comes from losing muscle and moving less. Strength training and daily activity help offset it.